<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			div {
				width: 100%;
				height: 300px;
				background-color: orange;
			}
			@media screen and (max-width:499px) {
				div {
					background-color: orange;
				}
			}
            /* 500px~700px 页面背景色变为red  phone*/
			@media screen and (min-width:500px) {
				div {
					background-color: red;
					font-size: 30px;
				}
			}
            /* 700px~900px 页面背景色变为yellow pad*/
			@media screen and (min-width:700px) {
				div {
					background-color: yellow;
					font-size: 20px;
				}
			}
            /* 大于900px 页面背景色变为blue pc*/
			@media screen and (min-width:900px) {
				div {
					background-color: blue;
					font-size: 12px;
				}
			}
		</style>
	</head>
	<body>
		<div>博为峰</div>
	</body>
</html>
